In electronics, an optocoupler, also called an opto-isolator, photocoupler, or optical isolator, is an electronic device designed to transfer electrical signals by utilizing light waves to provide coupling with electrical isolation between its input and output. The main purpose of an optocoupler is to prevent high voltages or rapidly changing voltages on one side of the circuit from damaging components or distorting transmissions on the other side. Commercially available optocouplers can withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to 10 kV/μs.
An optocoupler contains a source (emitter) of light, usually a near infrared light-emitting diode (LED), that converts electrical input signal into light, a closed optical channel (also called dielectrical channel), and a photosensor, which detects incoming light and either generates electric energy directly, or modulates electric current flowing from an external power supply. The photosensor can be a photoresistor, a photodiode, a phototransistor, a silicon-controlled rectifier (SCR) or a triac. Because LEDs can sense light in addition to emitting it, construction of symmetrical, bi-directional optocouplers are possible. An optocoupled solid state relay contains a photodiode optocoupler which drives a power switch, usually a complementary pair of MOSFET transistors. A slotted optical switch contains a source of light and a sensor, but its optical channel is open, allowing modulation of light by external objects obstructing the path of light or reflecting light into the sensor.
Most optocouplers are protected by a silicone encapsulant that is deposited around both the light source and photosensor. Optocouplers are typically manufactured by depositing an amount of silicone on one side of the optocoupler, flipping the optocoupler over, and then depositing another amount of silicone on the other side of the optocoupler. It can be appreciated that this multi-step process is both time-consuming and expensive.
It would be desirable to improve the process of manufacturing optocouplers and minimize the above-noted inefficiencies in current optocoupler manufacturing techniques.